The objective of this project is to evaluate factors important in the immediate and long term healing response to laser ablation in arterial tissue. Although many laser systems can ablate atherosclerotic plaque in vivo, there is little data on the biologic response of vascular tissue-to thermal and other lightinduced injuries. Experimental goals will start with the determination of the Arrhenius thermal damage integral as a function of temperature-time exposure for both arterial cell viability (endothelial and vascular smooth muscle) in tissue culture and arterial wall structural protein denaturation. The arterial intimal surfaces, irradiated by these lasers to achieve specific damage integrals, will be studied for several purposes: to determine how hospitable the surfaces become after thermal injury to endothelial cell attachment and migration, identify what effect the thermally denatured surfaces have on platelet adherence, and the effect of thermal damage on arterial wall compliance. This data can be useful to identify the optimal postlaser conditions for laser recanalization or the application of laser technology as an adjunct with other procedures.